The spermatozoon of arthropoda. XXIV. Sperm metamorphosis in the diplopod Polyxenus

Abstract The authors describe the spermiogenesis of Polyxenus lagurus, a diplopod, in the male genital ducts and the transformations the spermatozoon successively undergoes in the spermatheca. The spermatozoon in the male genital ducts looks like a little barrel devoid of centriole and of any kind of rudimentary flagellum whatever. The organelles are markedly modified; cross sections present an elongated, flattened nucleus, an X‐shaped body running parallel to it on the opposite side and two longitudinal mitochondrial strips interposed between them. The rest of this barrel‐shaped spermatozoon is filled with peculiar Golgi formations, the spongy chambers, which open outwards through little vents. In the spermatheca the spermatozoon is quite different: it is shaped like a long ribbon. The basic structure of the spermatozoon is formed by the double folding of part of the cortical layer of the barrel‐shaped spermatozoon. On the central part of this endo‐skeleton are longitudinally ranged the nucleus and the acrosome flanked on both sides by a thread of mitochondria. Even in this phase the sperm has no flagellum.